A: If you plan to eat and drink nothing, then, yes, it’s risky. It could cause dehydration and dangerously low blood sugar levels, which can make you pass out. If you’re otherwise healthy and still drink water, 100 percent fruit juice, and no-calorie beverages, you probably won’t suffer health consequences if you do it only for a day at a time every once in a while (not twice a week). But get your doctor’s OK first, and know that most of the weight lost will be water and muscle, not fat. Our advice: Forget the fast and make small changes you can live with for a lifetime.

Q:I need to lose 30 pounds. If I do will I go down a bra size?

A: Breast tissue is virtually all fat, so it shrinks when you lose weight. But exercises that build up chest muscles can help keep breasts looking full. Every other day, do Push-Ups (2–3 sets of as many as you can). Then do Chest Presses (2–3 sets of 12–15 reps): Lie on your back with a 5- to 8-pound weight in each hand, arms open, and elbows bent. Press weights up toward the ceiling, then lower.

Julie Upton, MS, RD, is a media resource for the American Dietetic Association.